When you turn your taps on in Nelson City, it's important to us that you get high-quality water to drink or use. We make sure that the water is treated and is piped to Nelson properties.
Our Utility Maintenance Contractors help us to do this. Fulton Hogan Ltd manages our water catchments and the Water Treatment Plant and Nelmac Ltd undertakes all work on the water distribution reticulation (e.g. the pipes to your homes).
In the hills behind Nelson City are our water catchments, that feed into the Maitai or Roding Rivers. Water from these rivers ends up at our treatment plant and then into our homes.
A part of our catchment includes a mineral belt, which contains iron and manganese. These elements can naturally react to the old cast iron pipes that make up part of the city’s water reticulation.
This reaction can create fine particles which, while harmless, can settle in the pipes.
These particles can be stirred up, by vibrations or accelerated flows. This could be from nearby construction work or a watermain break. If stirred up, the fine particles can cause the water to become discoloured.
Flushing the pipes:
To minimise the chance of this happening, we carry out Fire Hydrant Flushing. This normally occurs in areas of low demand, key junction points or known problem areas where the particles can build up.
Each hydrant is flushed between 5 to 10 minutes, depending on the location. This helps clear any fine particles that may have built up.
The current flushing program takes between 6 to 8 weeks to work its way across the whole city before it starts again, depending on reactive/emergency work that occurs during that time. This means that Nelmac are flushing across the whole city at least 6 times a year.
While this process does use water it is important to remove as much of the material as possible in order to limit its impact on the business and residential customers in the city.
Nelmac also undertake reactive flushing to manage and clear discoloured water issues as they get called in. This is over and above the planned preventative work.